Disc drives, such as magnetic storage disc drives, optical disc drives, compact disc (CD) drives, digital video disc (DVD) drives, and other types of disc drives that are commonly used in digital processing systems, generally include a disc mounted to a rotatable spindle, a spindle motor adapted to rotate the spindle, and motor control circuitry that is adapted to control the motor.
Portable digital processing systems that use such disc drives include, for example, laptop computers, portable CD players, portable DVD players, and MP3 audio players. These systems include a battery for providing power to the disc drive as well as other electronic components of the system that are collateral to the disc drive. These collateral electronic components include data processing electronics used to process the data stored on the recording medium of the disc drive, voltage regulators, battery chargers and other electronic components.
The limited power supply that is available for such portable digital processing systems is of continuous concern. Efforts are made to maximize battery life while minimizing sacrifices in performance using various power saving techniques.
The disc drives of such systems are often the largest consumers of battery power. In particular, the spindle motor of the disc drive consumes a large amount of power during startup routines, when the disc medium must be accelerated to an operating angular velocity, typically 5,400 RPM and greater for magnetic disc drive storage systems. The power consumed during such a startup routine depends, in part, upon the number of discs in the disc drive and the operational velocity that must be attained. The power consumed by the disc drive is exacerbated when the disc drive is frequently stopped and started. This commonly occurs with CD disc drives, DVD disc drives, and disc drives used in MP3 audio players. Although magnetic disc drive storage systems are fairly efficient at maintaining the operating speed, the spindle motor can unnecessarily consume a large amount of battery power during long idle periods when no transfer of data to or from the disc drive is occurring. As a result, it is common practice to shutdown the disc drive during these periods of non-use and restart it when a data exchange is desired.
When the disc drive is shutdown, the kinetic energy of the rotating disc or discs is generally lost to heat energy. Some magnetic disc drive storage systems convert the kinetic energy of the disc and spindle during an abrupt power loss into electrical energy by braking the spindle motor. The generated energy is then provided to other components of the disc drive to transport transducing heads, which are used to read and write data to the discs, into a shutdown position without damaging them or the disc media. Although these systems are effective in providing a controlled shutdown of the disc drive, they do not address issues relating to extending battery life of portable digital processing systems.
There is a continuing need to extend battery life in portable digital processing systems. One source of energy that is yet to be utilized to extend battery life is the kinetic energy of the rotating discs of the disc drive that is used in such systems. It would be desirable to convert this energy for use by electronic components that are collateral to the disc drive to conserve battery power.